The present invention relates to internal combustion engines; more particularly, to devices for controlling systems in an internal combustion engine; and most particularly, to a hydraulic control means for controlling the activation and deactivation of valve lifters in an internal combustion engine to engage and disengage selected cylinders from participating in the combustion of such an engine.
Internal combustion engines are well known. Such an engine may include a plurality of combustion cylinders, each containing a reciprocable piston connected to a common crankshaft by a connecting rod. In so-called four-stroke or four-cycle engines, each cylinder is provided with one or more intake valves for admitting fuel/air mixture to the cylinder and one or more exhaust valves for exhausting burned mixture from the cylinder. A sparking plug extending into each cylinder ignites the compressed fuel/air mixture at a predetermined time relative to the rotary position of the crankshaft. Typically, the intake valves are actuated by an intake camshaft operatively connected to the crankshaft and having a plurality of cam lobes radially disposed at varying predetermined angles to cause the intake valves to open and close at the proper preselected times during rotation of the crankshaft. The exhaust valves are similarly controlled by an exhaust camshaft. In some engines, the intake and exhaust cam lobes are provided on a single, common camshaft. In an overhead valve engine, the valves may be actuated directly by camshafts disposed on the head itself, or the camshaft(s) may be disposed within the engine block and may actuate the valves via a valve train including valve lifters, pushrods, and rocker arms. In V-style engines, alternate cylinders are disposed at an included central angle from the crankshaft bearing axis such that even-number cylinders are grouped into a first cylinder bank and odd-number cylinders are grouped into a second cylinder bank. A single camshaft disposed within the engine block may actuate all the valves in both cylinder banks. The longitudinal depression between the banks of a V-style engine, and below the intake manifold, is known in the art as the engine xe2x80x9cvalley.xe2x80x9d
In most prior art four-stroke internal combustion engines, the mutual relationships of the crankshaft, camshaft, and valves are mechanically fixed; that is, the valves are opened and closed fully and identically with every two revolutions of the crankshaft, fuel/air mixture is drawn into each cylinder in a predetermined sequence, ignited by the sparking plug, and the burned residue discharged. This sequence occurs irrespective of the rotational speed of the engine or the load being placed on the engine at any given time.
It is known that for much of the operating life of a multiple-cylinder engine, the load might be met by a functionally smaller engine having fewer firing cylinders, and that at low-demand times fuel efficiency could be improved if one or more cylinders of a larger engine could be withdrawn from firing service. It is known in the art to accomplish this by de-activating the valve train leading to preselected cylinders in any of various ways, such as by providing special valve lifters having internal locks which may be switched on and off either electrically or hydraulically.
It is a principal object of the present invention to provide an improved electric/hydraulic system for controlling the hydraulic locking and unlocking of deactivatable valve lifters in an internal combustion engine.
It is a further object of the invention to provide such a system wherein trapped air is automatically purged immediately upon engine startup and is prevented from re-entry during engine operation.
It is a still further object of the invention to provide such a system comprising a minimum number of components which then may be easilyfabricated.
It is a still further object of the invention to provide such a system which can reliably activate or deactivate selected valves within the time required for one revolution of an engine""s camshaft.
Briefly described, a hydraulic control system in accordance with the invention includes a hydraulic manifold assembly for controllably directing or withholding engine oil, provided under pressure by the engine oil pump, to an engine""s deactivation valve lifters to activate or deactivate the associated engine intake and exhaust valves. The assembly may be conveniently disposed, for example, in the valley of a V-style engine beneath the intake manifold. Passages to the valve lifters are controllably opened or closed by an electric solenoid activation control valve, such control valves being responsive to signals from a computerized engine control system. Preferably, the hydraulic manifold assembly comprises a top plate having a first pattern of channels formed in the underside thereof, and a bottom plate having a second such pattern formed in the upper surface thereof, such that when the top and bottom plates are matably joined the appropriate manifold is formed. In a presently preferred embodiment, a gasket plate having a pattern of bores therethrough and different patterns of resilient gasketing material around the bores applied to the upper and lower surfaces of the plate, is provided between the top and bottom plates to simplify fabrication of the top and bottom plates. Alternatively, the resilient gasketing material may be applied in appropriate patterns directly to the top and bottom plates. Solenoid control valves are disposed on the underside of the bottom plate and extend therethrough into the manifold to open and close their respective control passages in the manifold upon command. A dual-purpose lead frame retainer/connector both retains the control valves in the bottom plate and provides electrical connection to each control valve.